The objective of the proposed research is to produce new methods of studying the intermolecular structure and organization of membranes, using photo-electric effects in bilayer membranes. Experiments in our laboratory have shown that certain electrically charged azo, cyanine and phenol dyes sorb to membranes and induce transmembrane voltages when illiminated. The photo-voltage waveforms obtained with dyes from each of these groups vary with physical factors also known to modify the membranes' intermolecular structure. Additional experiments with azo, cyanine and phenol dyes are planned. Preliminary experiments with erythrosine (red dye number 3, a phenol dye) indicate this dye binds to positively charged amines and the photo-voltages induced provides a means of detecting these charged functional groups on membrane surfaces. High speed analogue apparatus constructed in our laboratory enable light induced electric charge displacements in membranes to be accurately detected with 10 ns resolution. Support is requested to cnstruct a digital data acquisition system, which will facilitate determining the photo-effect quantum efficiency for these dyes. Support is also requested to construct a current pulse apparatus which will allow external potential induced charge displacements in membranes to be followed with 40 ns resolution. This may be fast enough to follow potential induced dipole reorientations in membranes. This apparatus will be used in combined current pulse/light flash experiments on membranes.